As is well known in the art, an AWD (All Wheel Drive) vehicle can be provided with at least one hydraulic disc coupling for distributing the driving torque from the vehicle engine to all of the vehicle wheels. Especially, such a coupling may be provided in the drive line between the front axle and the wheels of the rear axle, most often in the vicinity of the rear axle differential.
Sometimes, it may be desirable to use the AWD vehicle in a FWD (Forward Wheel Drive) mode. In this case the coupling is disconnected, i.e. its discs are separated from each other.
By operating the vehicle with the coupling in a disconnect mode, rotating masses in the vehicle are reduced, leading to a lower fuel consumption.
In a practical case a propeller shaft of the vehicle, possibly including one or two bevel gear transmissions, has a hydraulic disc coupling at one end and a simple connect/disconnect clutch, for example a dog clutch, at the other end. In the disconnect mode both these couplings must be disconnected for obtaining the desired effect.
The present invention relates to a hydraulic system with a dog clutch, having a hydraulically operated dog clutch actuator as set out above.
A pump actuator system for an AWD hydraulic disc coupling is disclosed in WO 2011/043722 . In such a system the supply of hydraulic oil to the coupling piston is governed by the rotative speed of a pump. A similar system may be utilized for the operation of the dog clutch actuator.
It is of great importance that the disconnect/connect function is performed properly, so that the respective mode is reached as desired. There is thus a need to obtain a check in the form of a confirmation signal that the respective mode has been reached.